polymorphic kind inference off, turn on (off) with LANGUAGE pragma (N…

…o)PolyKinds

EHC/src/ehc/Base/Pragma.chs

@@ -41,6 +41,10 @@ data Pragma
   | Pragma_GenericDeriving                  -- turn on generic deriving (default)
   | Pragma_NoBangPatterns               	-- turn off bang patterns
   | Pragma_BangPatterns                  	-- turn on bang patterns (default)
+  | Pragma_NoPolyKinds               		-- turn off polymorphic kinds (default)
+  | Pragma_PolyKinds                  		-- turn on
+  | Pragma_NoOverloadedStrings         		-- turn off overloaded strings (default)
+  | Pragma_OverloadedStrings           		-- turn on
   | Pragma_ExtensibleRecords                -- turn on extensible records
   | Pragma_Fusion               			-- turn on fusion syntax
   | Pragma_OptionsUHC              			-- commandline options
@@ -69,6 +73,10 @@ allSimplePragmaMp
                   , Pragma_NoGenericDeriving
                   , Pragma_BangPatterns
                   , Pragma_NoBangPatterns
+                  , Pragma_NoPolyKinds         
+                  , Pragma_PolyKinds           
+                  , Pragma_NoOverloadedStrings 
+                  , Pragma_OverloadedStrings   
                   , Pragma_ExtensibleRecords
                   , Pragma_Fusion
                   ]
@@ -120,6 +128,10 @@ instance Serialize Pragma where
   sput (Pragma_NoBangPatterns           ) = sputWord8 8
   sput (Pragma_BangPatterns             ) = sputWord8 9
   sput (Pragma_OptionsUHC      a        ) = sputWord8 10 >> sput a
+  sput (Pragma_NoPolyKinds       		) = sputWord8 11
+  sput (Pragma_PolyKinds         		) = sputWord8 12
+  sput (Pragma_NoOverloadedStrings		) = sputWord8 13
+  sput (Pragma_OverloadedStrings 		) = sputWord8 14
   sget = do t <- sgetWord8
             case t of
               0  -> return Pragma_NoImplicitPrelude
@@ -135,6 +147,10 @@ instance Serialize Pragma where
               8  -> return Pragma_NoBangPatterns
               9  -> return Pragma_BangPatterns
               10 -> liftM  Pragma_OptionsUHC             sget
+              11 -> return Pragma_NoPolyKinds       
+              12 -> return Pragma_PolyKinds         
+              13 -> return Pragma_NoOverloadedStrings
+              14 -> return Pragma_OverloadedStrings 
 
 %%]
 

EHC/src/ehc/EH/Infer.cag

@@ -409,7 +409,7 @@ SEM Expr
                             .   gKiTvS              =   @tyKiUpdFreeTvarS
 %%]]
                             .   lQuTyGam            =   @tyGam_l_extra
-                            .   lQuTyKiGam_qu       =   tyKiGamQuantify @gKiTvS @lSubsTyKiGam
+                            .   lQuTyKiGam_qu       =   tyKiGamQuantify @lhs.opts @gKiTvS @lSubsTyKiGam
                             .   lQuTyKiGam_ex       =   tyKiGamInst1Exists @lUniq3 @lQuTyKiGam_qu
                             .   lQuTyKiGam          =   @lQuTyKiGam_ex_extra
                             .   lQuTyKiGam_ex_extra =   gamUnion @extraTyKiGam @lQuTyKiGam_ex
@@ -437,7 +437,7 @@ SEM Expr
 %%[(8 hmtyinfer)
 SEM Expr
   | Let         loc         .   (lQuTyKiGam_qu,quTyKiVarMp, cycTyKiVarMp_l)
-                                                    :=  tyKiGamQuantifyWithVarMp @decls.kiVarMp @gKiTvS @tyKiGam_l_
+                                                    :=  tyKiGamQuantifyWithVarMp @lhs.opts @decls.kiVarMp @gKiTvS @tyKiGam_l_
                             .   bodyTyKiVarMp1      =   @quTyKiVarMp `varUpd` @decls.kiVarMp
                             .   (lQuTyKiGam_ex,exTyKiVarMp2)
                                                     :=  tyKiGamInst1ExistsWithVarMp @bodyTyKiVarMp1 @lUniq3 @lQuTyKiGam_qu
@@ -679,7 +679,7 @@ SEM Decl
 
 %%[(6 hmtyinfer)
 SEM Decl
-  | KiSig       loc         .   sigKi               =   tyKiQuantify (const False) @kiExpr.ki
+  | KiSig       loc         .   sigKi               =   tyKiQuantify True (const False) @kiExpr.ki
 %%]
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

EHC/src/ehc/Gam/Quantify.chs

@@ -5,7 +5,7 @@
 %%[(3 hmtyinfer) module {%{EH}Gam.Quantify}
 %%]
 
-%%[(3 hmtyinfer) hs import ({%{EH}Base.Common})
+%%[(3 hmtyinfer) hs import ({%{EH}Base.Common}, {%{EH}Opts.Base})
 %%]
 %%[(3 hmtyinfer) hs import ({%{EH}Ty})
 %%]
@@ -86,16 +86,16 @@ valGamQuantifyWithVarMp doQuant tyKiGam tvKiVarMp gamVarMp globTvS prL valGam
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 %%[(6 hmtyinfer || hmtyast).tyKiGamQuantify export(tyKiGamQuantify)
-tyKiGamQuantify :: TyVarIdS -> TyKiGam -> TyKiGam
-tyKiGamQuantify globTvS
-  = gamMap (\(n,k) -> (n,k {tkgiKi = tyKiQuantify (`Set.member` globTvS) (tkgiKi k)}))
+tyKiGamQuantify :: EHCOpts -> TyVarIdS -> TyKiGam -> TyKiGam
+tyKiGamQuantify opts globTvS
+  = gamMap (\(n,k) -> (n,k {tkgiKi = tyKiQuantify (ehcOptPolyKinds opts) (`Set.member` globTvS) (tkgiKi k)}))
 %%]
 
 %%[(8 hmtyinfer || hmtyast).tyKiGamQuantifyWithVarMp -6.tyKiGamQuantify export(tyKiGamQuantifyWithVarMp)
-tyKiGamQuantifyWithVarMp :: {- TyKiGam -> VarMp -> -} VarMp -> TyVarIdS -> TyKiGam -> (TyKiGam,VarMp,VarMp)
-tyKiGamQuantifyWithVarMp {- tyKiGam tvKiVarMp -} gamVarMp globTvS gam
+tyKiGamQuantifyWithVarMp :: EHCOpts -> VarMp -> TyVarIdS -> TyKiGam -> (TyKiGam,VarMp,VarMp)
+tyKiGamQuantifyWithVarMp opts {- tyKiGam tvKiVarMp -} gamVarMp globTvS gam
   = tyKiGamDoWithVarMp
-      (\_ (t,tyCycMp) m cycMp -> (tyKiQuantify {- (tvarKi tyKiGam tvKiVarMp gamVarMp) -} (`Set.member` globTvS) t,m,tyCycMp `varUpd` cycMp))
+      (\_ (t,tyCycMp) m cycMp -> (tyKiQuantify (ehcOptPolyKinds opts) {- (tvarKi tyKiGam tvKiVarMp gamVarMp) -} (`Set.member` globTvS) t,m,tyCycMp `varUpd` cycMp))
       gamVarMp emptyVarMp gam
 %%]
 

EHC/src/ehc/Opts.chs

@@ -73,15 +73,19 @@ ehcOptUpdateWithPragmas pragmas opts
   = foldr (\p om@(o,modf) -> maybe om (\o -> (o,True)) $ upd p o) (opts,False) (Set.toList pragmas)
   where upd pragma opts
           = case pragma of
-              Pragma_NoGenericDeriving  -> Just $ opts { ehcOptGenGenerics          = False }
-              Pragma_GenericDeriving    -> Just $ opts { ehcOptGenGenerics          = True  }
-              Pragma_NoBangPatterns     -> Just $ opts { ehcOptBangPatterns         = False }
-              Pragma_BangPatterns       -> Just $ opts { ehcOptBangPatterns         = True  }
-              Pragma_ExtensibleRecords  -> Just $ opts { ehcOptExtensibleRecords    = True  }
-              Pragma_Fusion             -> Just $ opts { ehcOptFusion               = True  }
-              Pragma_OptionsUHC o       -> fmap (\o -> o {ehcOptCmdLineOptsDoneViaPragma = True}) mo
-                                        where (mo,_,_) = ehcCmdLineOptsApply (words o) opts
-              _                         -> Nothing
+              Pragma_NoGenericDeriving  	-> Just $ opts { ehcOptGenGenerics          = False }
+              Pragma_GenericDeriving    	-> Just $ opts { ehcOptGenGenerics          = True  }
+              Pragma_NoBangPatterns     	-> Just $ opts { ehcOptBangPatterns         = False }
+              Pragma_BangPatterns       	-> Just $ opts { ehcOptBangPatterns         = True  }
+              Pragma_NoOverloadedStrings	-> Just $ opts { ehcOptOverloadedStrings	= False }
+              Pragma_OverloadedStrings		-> Just $ opts { ehcOptOverloadedStrings	= True  }
+              Pragma_NoPolyKinds     		-> Just $ opts { ehcOptPolyKinds         	= False }
+              Pragma_PolyKinds       		-> Just $ opts { ehcOptPolyKinds         	= True  }
+              Pragma_ExtensibleRecords  	-> Just $ opts { ehcOptExtensibleRecords    = True  }
+              Pragma_Fusion             	-> Just $ opts { ehcOptFusion               = True  }
+              Pragma_OptionsUHC o       	-> fmap (\o -> o {ehcOptCmdLineOptsDoneViaPragma = True}) mo
+                                        	where (mo,_,_) = ehcCmdLineOptsApply (words o) opts
+              _                         	-> Nothing
 %%]
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

EHC/src/ehc/Opts/Base.chs

@@ -147,6 +147,9 @@ data EHCOpts
       ,  ehcOptImmQuit        ::  Maybe ImmediateQuitOption
       ,  ehcOptDebug          ::  Bool              -- debug info
       ,  ehcStopAtPoint       ::  CompilePoint      -- stop at (after) compile phase
+%%[[6
+      ,  ehcOptPolyKinds	  ::  Bool              -- allow kind polymorphism
+%%]]
 %%[[7
       ,  ehcOptExtensibleRecords
       						  ::  Bool
@@ -241,7 +244,8 @@ data EHCOpts
       ,  ehcOptCPP            ::  Bool              -- do preprocess with C preprecessor CPP
       ,  ehcOptUseAssumePrelude                     -- use & assume presence of prelude
                               ::  Bool
-      ,  ehcOptPackageSearchFilter   ::  [PackageSearchFilter]  -- description of what to expose from package database
+      ,  ehcOptPackageSearchFilter 
+      					 	  ::  [PackageSearchFilter]  -- description of what to expose from package database
       ,  ehcOptOutputDir      ::  Maybe String      -- where to put output, instead of same dir as input file
       ,  ehcOptKeepIntermediateFiles
                               ::  Bool              -- keep intermediate files
@@ -251,6 +255,8 @@ data EHCOpts
       ,  ehcOptCmdLineOpts    ::  CmdLineOpts       -- options from the commandline and pragma for such options
       ,  ehcOptCmdLineOptsDoneViaPragma
       						  ::  Bool       		-- options via OPTIONS_UHC pragma have been set
+      ,  ehcOptOverloadedStrings
+      						  ::  Bool              -- allow overloaded strings
 %%]]
       }
 %%]
@@ -285,6 +291,11 @@ emptyEHCOpts
       ,  ehcOptImmQuit          =   Nothing
       ,  ehcOptDebug            =   False
       ,  ehcStopAtPoint         =   CompilePoint_All
+%%[[6
+      ,  ehcOptPolyKinds	    =   True
+%%][99
+      ,  ehcOptPolyKinds	    =   False
+%%]]
 %%[[7
       ,  ehcOptExtensibleRecords=   True
 %%][99
@@ -393,6 +404,7 @@ emptyEHCOpts
       ,  ehcOptCmdLineOpts      =   []
       ,  ehcOptCmdLineOptsDoneViaPragma
                                 =   False
+      ,  ehcOptOverloadedStrings=   False
 %%]]
       }
 %%]

EHC/src/ehc/Ty/Trf/Quantify.cag

@@ -89,13 +89,19 @@ tyQuantifyOuter tvKi tvIsBound ty
 %%]
 
 %%[(6 hmtyinfer || hmtyast) -3.valTyQuantify hs export(tyKiQuantify,valTyQuantify)
-tyKiQuantify :: TvIsBound -> Ty -> Ty
-tyKiQuantify tvIsBound ty -- = tyQuantify' tvIsBound tyQu_Forall {- tyQu_KiForall -} ty
+-- | Quantify kind, i.e. add universal quantifier for free tvars when kind polymorphism is allowed, otherwise just *
+tyKiQuantify
+  :: Bool			-- ^ kind polymorphism on (for inference steered by PolyKinds pragma)
+     -> TvIsBound
+     -> Ty
+     -> Ty
+tyKiQuantify polyKinds tvIsBound ty -- = tyQuantify' tvIsBound tyQu_Forall {- tyQu_KiForall -} ty
   = tqoTy $ tyQuantifyWithOpts opts ty
   where opts = defaultTyQuOpts
-                  { tqoptAllowInnerQuant = False
-                  , tqoptTvIsBound       = tvIsBound
-                  , tqoptBaseQuant       = tyQu_Forall
+                  { tqoptAllowInnerQuant 	= False
+                  , tqoptTvIsBound       	= tvIsBound
+                  , tqoptBaseQuant       	= tyQu_Forall
+                  , tqoptQuantVarDefaultsTo	= if polyKinds then Nothing else Just kiStar
                   }
 
 valTyQuantify :: (TyVarId -> Ty) -> TvIsBound -> Ty -> Ty
@@ -129,12 +135,13 @@ tyQuantify' tvIsBound baseQuant ty
 data TyQuOpts
   = TyQuOpts
       { tqoptTvIsBound			:: TvIsBound
+      , tqoptQuantVarDefaultsTo	:: !(Maybe Ty)				-- ^ if provided, not quantification takes place but var defaults to this
 %%[[4
-      , tqoptAllowInnerQuant	:: Bool
+      , tqoptAllowInnerQuant	:: !Bool
 %%]]
 %%[[6
-      , tqoptBaseQuant			:: TyQu
-      , tqoptTvL1				:: TyVarId -> Ty		-- mapping of tvar to 1 higher metalevel ty (i.e. kind)
+      , tqoptBaseQuant			:: !TyQu
+      , tqoptTvL1				:: TyVarId -> Ty			-- ^ mapping of tvar to 1 higher metalevel ty (i.e. kind)
 %%]]
 %%[[9
       , tqoptQuRanks 			:: [Int]
@@ -145,6 +152,7 @@ defaultTyQuOpts :: TyQuOpts
 defaultTyQuOpts
   = TyQuOpts
       (const False)
+      Nothing
 %%[[4
       True
 %%]]
@@ -363,17 +371,33 @@ tvarsToQuantL1 boundablesL tvIsBound
 %%]
 
 %%[(4 hmtyinfer || hmtyast).tvarsToQuant hs
-tvarsToQuant :: TyQuOpts -> Bool -> TvCatMp -> (TyVarId -> Bool) -> TvLevIsBound -> TyVarIdS -> (TyVarIdsToBind,TyVarIdsToBind,TyVarIdsToBind,TvLevIsBound)
+-- | Compute bindable tvars
+tvarsToQuant
+  :: TyQuOpts
+     -> Bool
+     -> TvCatMp
+     -> (TyVarId -> Bool)
+     -> TvLevIsBound			-- ^ 'is already bound?'
+     -> TyVarIdS
+     -> ( TyVarIdsToBind		-- ^ to bind universal, on this level
+        , TyVarIdsToBind		-- ^ to bind existential
+        , TyVarIdsToBind		-- ^ to bind universal, 1 level higher
+        , TvLevIsBound			-- ^ updated 'is already bound?'
+        , VarMp					-- ^ the tvars which are defaulted
+        )
 tvarsToQuant opts isQuLoc _ mayQuFx tvIsBound tvS
   =  if isQuLoc
      then  let boundablesS = tvNotBound 0 tvIsBound tvS
 %%[[4
                boundablesL = Set.toList boundablesS
                tvIsBound'  = tvBoundAddS 0 boundablesS tvIsBound
 %%][6
-               boundablesL                = [ (v,{- trm "tvarsToQuant" (\k -> v >|< "::" >|< k) $ -} tqoptTvL1 opts v) | v <- Set.toList boundablesS ]
-               (boundablesL1L,_,tvIsBound') = tvarsToQuantL1 boundablesL (tvBoundAddS 0 boundablesS tvIsBound)
-               -- tvIsBound'  = tvBoundAddS (boundablesS `Set.union` boundablesL1S) tvIsBound
+               (boundablesL,boundablesL1L,tvIsBound',defaultedVarMp)
+                 | isJust mbDf = ([]         , [] , tvIsBound, assocTyLToVarMp [ (v,df) | (v,_) <- boundablesL ])
+                 | otherwise   = (boundablesL, b1L, isb      , emptyVarMp                                       )
+                 where mbDf@(~(Just df)) = tqoptQuantVarDefaultsTo opts
+                       (b1L,_,isb) = tvarsToQuantL1 boundablesL (tvBoundAddS 0 boundablesS tvIsBound)
+                       boundablesL = [ (v, tqoptTvL1 opts v) | v <- Set.toList boundablesS ]
 %%]]
            in ( boundablesL
               , []
@@ -383,8 +407,9 @@ tvarsToQuant opts isQuLoc _ mayQuFx tvIsBound tvS
               , boundablesL1L
 %%]]
               , tvIsBound'
+              , defaultedVarMp
               )
-     else  ([],[],[],tvIsBound)
+     else  ([],[],[],tvIsBound,emptyVarMp)
 %%]
 
 %%[(6_4 hmtyinfer || hmtyast).tvarsToQuant -4.tvarsToQuant hs
@@ -417,18 +442,18 @@ tvMayQuFx qu fxTvM isQuFxLoc tv
 ATTR AllTy [ tvIsBound: {TvLevIsBound} | | ]
 
 SEM TyAGItf
-  | AGItf       loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound)
+  | AGItf       loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound,defaultedVarMpNew)
                                                         =   tvarsToQuant @lhs.opts True @fxTvM
                                                                          (const False)
                                                                          (tvIsBound2L0 $ tqoptTvIsBound @lhs.opts) @qHereTvS
 
 SEM Ty
-  | App Var     loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound)
+  | App Var     loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound,defaultedVarMpNew)
                                                         =   tvarsToQuant @lhs.opts @isQuLoc @lhs.fxTvM
                                                                          (tvMayQuFx @hereQu @lhs.fxTvM @isQuFxLoc)
                                                                          @lhs.tvIsBound @qHereTvS
   | TBind       loc         .   tvIsBoundQu             =   tvBoundAddS 0 @introTVarS @lhs.tvIsBound
-                            .   (qBndTvs,qBndExTvs,qBndL1TvsOther,tvIsBound)
+                            .   (qBndTvs,qBndExTvs,qBndL1TvsOther,tvIsBound,defaultedVarMpNew)
                                                         =   tvarsToQuant @lhs.opts @isQuLoc @lhs.fxTvM
                                                                          (tvMayQuFx @hereQu @lhs.fxTvM @isQuFxLoc)
                                                                          @tvIsBoundQu @qHereTvS
@@ -445,13 +470,13 @@ SEM Ty
 
 %%[(9 hmtyinfer || hmtyast)
 SEM Ty
-  | App Var     loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound)
+  | App Var     loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound,defaultedVarMpNew)
                                                         :=  tvarsToQuant @lhs.opts @isQuLoc @lhs.fxTvM (tvMayQuFx @hereQu @lhs.fxTvM @isQuFxLoc) @lhs.tvIsBound @qHereTvS
 %%]
 
 %%[(9 hmtyinfer || hmtyast)
 SEM Ty
-  | Pred        loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound)
+  | Pred        loc         .   (qBndTvs,qBndExTvs,qBndL1Tvs,tvIsBound,defaultedVarMpNew)
                                                         =   tvarsToQuant @lhs.opts @isQuLoc @lhs.fxTvM (const False) @lhs.tvIsBound @qHereTvS
 %%]
 
@@ -460,6 +485,24 @@ SEM Ty
   | Lam         loc         .   tvIsBound               =   tvBoundAddS 0 @introTVarS @lhs.tvIsBound
 %%]
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% Mapping for defaulting tyvars
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%[(4 hmtyinfer || hmtyast)
+ATTR AllTy [ defaultedVarMp: VarMp | | ]
+
+SEM TyAGItf
+  | AGItf		loc			.	defaultedVarMp	=	@defaultedVarMpNew
+
+SEM Ty
+  | App Var TBind
+%%[[9
+    Pred
+%%]]
+  				loc			.	defaultedVarMp	=	@defaultedVarMpNew `varUpd` @lhs.defaultedVarMp
+%%]
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%% Which quantifier to use for quantification
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -520,7 +563,7 @@ SEM TyAGItf
   | AGItf       loc         .   quTyBase        =   @ty.quTy
 
 SEM Ty
-  | Var         loc         .   quTyBase        =   Ty_Var @tv @categ.quTy
+  | Var         loc         .   quTyBase        =   maybe (Ty_Var @tv @categ.quTy) id $ varmpTyLookup @tv @lhs.defaultedVarMp
   | App         loc         .   quTyBase        =   Ty_App @func.quTy @arg.quTy
   | TBind       loc         .   quTyBase        =   
 %%[[4

EHC/test/regress/99/KindSig2.hs

@@ -3,6 +3,8 @@
    expected: error because U's kind is too general for Functor
 ---------------------------------------------------------------------------------------- -}
 
+{-# LANGUAGE PolyKinds #-}
+
 module KindSig2 where
 
 -- the signature would make U acceptable for Functor

EHC/test/regress/99/PolyKinds1.hs

@@ -0,0 +1,18 @@
+{- ----------------------------------------------------------------------------------------
+   what    : poly kind inference
+   expected: ok
+---------------------------------------------------------------------------------------- -}
+
+{-# LANGUAGE PolyKinds #-}
+
+module PolyKinds1 where
+
+data Proxy t = Proxy
+
+class Foo t where
+  bar :: Proxy t -> Int
+
+instance Foo Int  where bar _ = 0
+instance Foo []   where bar _ = 0
+
+main = return ()

EHC/test/regress/99/PolyKinds2.hs

@@ -0,0 +1,18 @@
+{- ----------------------------------------------------------------------------------------
+   what    : poly kind inference
+   expected: not ok, because of NoPolyKinds
+---------------------------------------------------------------------------------------- -}
+
+{-# LANGUAGE NoPolyKinds #-}
+
+module PolyKinds2 where
+
+data Proxy t = Proxy
+
+class Foo t where
+  bar :: Proxy t -> Int
+
+instance Foo Int  where bar _ = 0
+instance Foo []   where bar _ = 0
+
+main = return ()